If photonics is ever to displace or supplement electronics in microprocessors, the operations we perform on electrons need to be replicated on photons. A group at NIST is the latest to demonstrate a photonic diode – a device that passes light in one direction only, similarly to how diodes pass electrons in one direction only. …

Re: Useful!

Re: Useful!

In the 1970's several defense contractors worked on systems capable of detecting optics used to aim weapons, everything from tanks to snipers, and when detected the system would fire a laser into the optics to blind it. It worked by sensing light that entered the optics, then reflected back off of the sensor, (be it human or machine) and back out the optics. However it was later determined that using a laser to blind a human violated the Geneva convention, so instead it was used to control lethal weapons. I remember thinking how idiotic it was that it was not okay to blind a solider, but it was okay to kill him.

So a material like this could be used to block reflected light from going back out the optics and revealing the location of a sniper, tank, or other military asset.

Re: Useful!

Re: Useful!

There is a restaurant in Darwin (Australia) where the urinal in the men's toilet is a wall made of a one-way mirror. It is quite disconcerting to see all the diners in front of you while you get your todger out and piss towards them. Even though you *know* they can't see you, the fact that you can clearly see them makes the experience very strange indeed.

This may be only tangentially relevant but I couldn't help mentioning it anyway.

Re: Sir

"What about semi-light-passing materials?"

If you read carefully, it said that the "blocking" direction passed light, but at only one-thirtieth of the original intensity. This is barely above the level required to actually detect a difference reliably, in the field.

Re: Sir

Yeah!

How about using a magnestrictive or piezo substrate...

then you could vary the width between the grating and presumably change the amount of light for a given frequency in the forward direction. Not a truly photonic device but tall oaks from little acorns and all that.

Re: How about using a magnestrictive or piezo substrate...

Sniper scopes

"Do sniper scopes have a problem with transmitting light in the wrong direction?"

In fact, they can. If you ever worked surveying using a transit or theodolite, then as the rod carrier, you can often tell the fellow on the instrument when the axis of the scope traverses your line of site. The viewing end of a rifle scope and the shooter's face should be well shaded, otherwise the optic can gather light reflected off the shooter's face and "aim" it down the scope in a beam at whatever what ever he is viewing. From a distance, the scope appears to disappear and an odd circular patch of light will appear. It won't be brilliant like reflection, but the oddity can attract attention.